1. Field of the Invention
The present invention relates to a synthetic resin-made fastening-limiting device employed for limiting a fastening force of a joint fastening member in case of fastening a connection portion for connecting a pipe to a pipe receiving port on the side of a joint by means of the fastening member. The screw amount of the fastening member is appropriately adjusted, whereby the fastening-limiting device ensures the sealing property of the connection portion between the pipe receiving port and the pipe and prevents the pipe from slipping out of the pipe receiving port.
2. Description of the Prior Art
A pipe for transporting a fluid, which is used in a semiconductor production process, is often required to have the particularity of the use environment such as chemical resistance and corrosion resistance. In consideration of the particularity of the use environment, a synthetic resin-made pipe which has certain properties is used as pipes of this kind. Similarly, as the material of joints which are interposed in many connecting and branching portions of such a pipe (including joints which are integrally attached to valves and the like connected to the pipe), used is synthetic resin having certain properties.
Such a connection structure is often employed in which, by the fastening force exerted by a fastening member screwed to a pipe receiving port on the side of the joint, the pipe inserted into the pipe receiving port is prevented from accidentally slipping off and the sealing property of the connection portion is ensured. In the connection structure, the function of preventing accidental slipping-off of the pipe due to the fastening of the fastening member, and the performance of ensuring the sealing property of the pipe connection portion are exerted only after the contact pressure against the connection portion, which is generated by the fastening of the fastening member, reaches a reference contact pressure.
When such a connection structure is employed, conventionally, means for defining the degree of the fastening force of the fastening member to an appropriate level in order to prevent the pipe from slipping off and ensure the sealing property is realized by a method such as that in which the fastening member is screwed by using a torque wrench, or that in which, when the fastening member is to be screwed to the pipe receiving port, the fastening member is caused to make a predetermined number of rotations.
However, such methods including the method in which a torque wrench is used, and that in which the fastening member makes a predetermined number of rotations have a problem in that these methods are cumbersome and require skill.
When existence/nonexistence of a forge of fastening of the fastening member, or adequateness of the fastening state of the fastening member is to be determined, cumbersome checking work must be conducted using tools and jigs. Therefore, it is difficult to completely eliminate an accident due to a forge of fastening or a failure of fastening.
The present invention has been developed; and in view of the above mentioned circumstances and problems.
It is an object of the present invention to enable an appropriate screw amount of a fastening member to be determined without using a prior art method that is cumbersome and requires skill.
It is another object of the present invention that an appropriate screw amount of a fastening member at which the above-mentioned reference contact pressure is obtained can be determined without using a prior art method that is cumbersome and requires skill.
It is still another object of the present invention that a forge of fastening of a fastening member, or adequateness of the fastening state of the fastening member can be checked easily and rapidly.
It is a still further object of the present invention that a fastening member is prevented from being fastened at a degree exceeding an allowable fastening limit.
A synthetic resin-made fastening-limiting device for a joint fastening member, employed with a fastening member for fastening a pipe which is inserted into a pipe receiving port on the side of a joint, comprises:
a ring portion which is fittable onto an outside of the pipe receiving port;
a first abutting portion disposed on one end face in an axial direction of the ring portion, for abutting against a reference face disposed on the side of the joint;
a protrusion which protrudes from another end face in the axial direction of the ring portion; and
a second abutting portion which is formed by a tip end of the protrusion, for abutting against a confronting portion when the fastening member having said confronting portion confronting the reference face is screwed to the pipe receiving port.
In the fastening-limiting device of the present invention, when the fastening member is screwed to the pipe receiving port onto which the ring portion is fitted, the protruding confronting portion of the fastening member pushes the fastening-limiting device to cause the first abutting portion to abut against the reference face on the side of the joint. Under this state, in the fastening-limiting device, the first abutting portion abuts against the reference face on the side of the joint, and the second abutting portion abuts against the confronting portion on the side of the fastening member.
In case that the fastening member is further screwed from this condition, a force required for screwing is increased, which is recognized by the operator. Then, the screw amount of the fastening member can be determined without using the prior art method that is cumbersome and requires skill.
Preferably, a distance in the axial direction of the ring portion between the first and second abutting portions is equal to a gap between the reference face and the confronting portion at the timing when a screw amount of the fastening member to the pipe receiving port reaches an appropriate value.
In the fastening-limiting device having this configuration, when the first abutting portion abuts against the reference face on the side of the joint, and the second abutting portion abuts against the confronting portion on the side of the fastening member, a gap between the reference face and the confronting portion of the fastening member is equal to a distance between the first abutting portion and the second abutting portion, whereby the screw amount of the fastening member reaches an appropriate amount.
Preferably, a distance between the first abutting portion and the other end face in the axial direction of the ring portion is equal to the gap between the reference face and the confronting portion at the time when the screw amount of the fastening member to the pipe receiving port reaches a limit of screwing, and the ring portion is provided with a recessed portion allowing the protrusion pressed by the confronting portion to fall down.
In this configuration, the first abutting portion abuts against the reference face on a side of the joint, and the second abutting portion abuts against the confronting portion of the fastening member. Thereafter, the fastening member is further a screwed to make the protrusion fall down into the recessed portion. As a result, the first abutting portion abuts against the reference face on a side of the joint, and the other end face in the axial direction of the ring portion abuts against the confronting portion on a side of the fastening member. In this time, the gap between the reference face and the confronting portion of the fastening member is equal to the distance between the first abutting portion and the other end face in the axial direction of the ring portion, whereby the screw amount of the fastening member reaches the limit so as to make it impossible to screw the fastening member.
The screwing position of the fastening member at the time when the screw amount of the fastening member reaches the appropriate value is indicated as xe2x80x9cthe initial appropriate positionxe2x80x9d, and the screwing position of the fastening member at the time when the screw amount of the fastening member reaches the limit of screwing is indicated as xe2x80x9cthe limit appropriate position.xe2x80x9d The screw amount of the fastening member at the time when the fastening member is located between the initial appropriate position and the limit appropriate position corresponds to an appropriate screw amount of the fastening member. When the fastening member is screwed by such an appropriate screw amount, it is possible to obtain the function of preventing accidental slipping-off of the pipe due to fastening of the fastening member, and the contact pressure at which the sealing property of the pipe connection portion is ensured.
Preferably, the confronting portion is protrusively formed, and the ring portion is provided with an engaging portion engaged with a projection disposed on the pipe receiving port, for checking a rotation of the ring portion. In this configuration, the engaging portion of the ring portion is engaged with a projection of the pipe receiving port, whereby the rotation of the ring portion with respect to the pipe receiving port is checked. Therefore, even though the confronting portion of the fastening member screwed to a pipe receiving port abuts against the second abutting portion, the ring portion is not co-rotated together with the fastening member. Consequently, in case that the confronting portion is protrusively formed, the fastening member is screwed thereby having the effect wherein the protrusive confronting portion touches the protrusion of the fastening-limiting device so as to snap it. Therefore, the fastening member is further screwed from the initial appropriate position, whereby the protrusion is snapped by the confronting portion of the fastening member to produce a sound, before the fastening member reaches the limit appropriate position. Thus, the sound is recognized by the operator so that he can recognize that the screw amount of the fastening member reaches an appropriate range.
To the contrary, when each of the first abutting portion and the second abutting portion does not abut against the reference face or the confronting portion, a gap exists between the ring portion and reference face, or between the second abutting portion and the confronting portion. When the gap is visually observed, therefore, it is possible to immediately recognize that the fastening member is not screwed by an appropriate amount. When such a gap cannot be visually observed, it is possible to immediately recognize that the fastening member is screwed by an appropriate amount.
Preferably, the recessed portion and the other recessed portion are formed on either side of the protrusion of the ring portion, and the engaging portion is disposed on a recessed-entrance surface of the other recessed portion. Thus, for example, the joint has two pipe receiving ports oppositely protruding, the same fastening-limiting device may be oppositely employed for each pipe receiving port. In other words, the ring portion is fitted onto the pipe receiving port protruding to the left in a state wherein the protrusion is protruded to the left, and the ring portion is fitted onto the pipe receiving port protruding to the right in a state wherein the protrusion is protruded to the right. Then, it has the same effects as the above mentioned ones even though both directions of screwing the fastening member onto the right and left pipe receiving ports are oriented in a clockwise direction. Especially, in the fastening-limiting device having the two recessed portions symmetrically formed on either side of the projection so as to sandwich the projection, even though the fastening-limiting device is fitted onto either left or right pipe receiving port, both use states are similar.
Preferably, a length in a circumferential direction of the ring portion of the other recessed portion is longer than that in a circumferential direction of the pipe receiving port of the projection.
When the ring portion is fitted onto the pipe receiving port, this facilitates the recessed portion being fitted onto the projection without exactly positioning the recessed portion having the engaging portion with respect to the projection of the pipe receiving portion.
The fastening-limiting device mentioned above adopts a configuration wherein, when the fastening member screwed to the pipe receiving port reaches the limit appropriate position, the protrusion falls down into the recessed portion of the ring portion, whereby the confronting portion of the fastening member abuts against the other end face in the axial direction of the ring portion. Alternatively, the protrusion may be disposed on the elastically deformable beam portion on the ring portion by forming the void space on the ring portion.
Thus, the effect of making the operator recognize that the fastening member is screwed to the initial appropriate position is exhibited in the same manner as the above configuration. In the same way, it can be recognized whether the fastening member is screwed by an appropriate amount or not.
Furthermore, it is recognized by a sound that the fastening member is screwed by an appropriate amount, as below. Namely, the first abutting portion of the fastening-limiting device pushed by the fastening member abuts against the reference face on a side of the joint. Thereafter, the fastening member is further screwed, and the protrusive confronting portion of the fastening member pushes the protrusion of the fastening-limiting device, thereby causing elastic deformation of the beam portion. Consequently, the effect is performed, wherein the confronting portion overrides the protrusion so as to make the beam portion retrieve in an original shape. When the fastening member is further screwed from the initial appropriate position, until it reaches the limiting appropriate position, the protrusion is snapped by the confronting portion of the fastening member so as to produce a sound. Therefore, the operator recognizes the sound thereby making it possible to recognize that the screw amount of the fastening member reaches the appropriate range. Furthermore, after the fastening member reaches the limit appropriate position, the ring portion checks forward movement of the fastening member. As a result, the fastening member cannot be screwed.
In the fastening-limiting device whose projection is disposed on the beam portion, the ring portion is provided with the engaging portion engaged with the projection disposed on the pipe receiving port, for checking a rotation of the ring portion. Preferably, the engaging portion is disposed on the peripheral wall surface of the void space. This does not require providing the engaging portions on the void space and the other area, leading to simplifying the structure of the fastening-limiting device at the same time while limiting the reduction of the strength of the ring portion.
Preferably, the protrusion can retract to the back portion of the other end face in the axial direction of the ring portion owing to the elastic deformation of the beam portion. When the fastening member is screwed to the limit appropriate position, it is never caused that the protrusion of the ring portion checks the screw of the fastening member.
Preferably, the circumferential length of the ring portion of the void space is longer than that of the pipe receiving port of the projection. When the ring portion is fitted onto the pipe receiving port, this facilitates the recessed portion being fitted onto the projection without exactly positioning the recessed portion having the engaging portion with respect to the projection of the pipe receiving portion.
Preferably, a protrusive piece is radially inwardly disposed at a predetermined place in a circumferential direction of the ring portion, and the pipe receiving port on a side of the joint is provided with an annular groove for holding the protrusive piece. In this configuration, the protrusive piece disposed on the ring portion is held by the annular groove of the pipe receiving port of the joint, thus preventing the fastening-limiting device from slipping off the pipe receiving port easily. As a result, this never causes a state wherein the fastening-limiting device slips off in connecting pipes so as to result in decrease of the operation efficiency.
As described above, when the fastening-limiting device of the invention is used, an appropriate screw amount of the fastening member at which the reference contact pressure is obtained can be surely determined without dispersion and without using a prior art method that is cumbersome and requires skill. Especially, the ring portion is never rotated with respect to the pipe receiving port of the joint. This ensures a performance wherein the protrusive confronting portion of the fastening member snaps the protrusion protruding from the ring portion. Then, the operator can recognize exactly the appropriate screw amount of the fastening member by touch and the sound produced at the moment. Furthermore, the fastening member screwed by an appropriate amount can be further screwed to the limit appropriate position.